Device for jet propulsion through water



y 7, 1953 w. K. coxE ETAL DEVICE FOR JET PROPULSION THROUGH WATER Filed April 29, 1948 2 Sheets-Sheet 1 finial con.

IN VEN TOR. WIN THROP K. COXE m 0 WW M J M M; m@

y 7, 1953 w. K. COXE ETAL 2,644,297

DEVICE FOR JET PROPULSION THROUGH WATER Filed April 29, 1948 2 Sheets-Sheet 2 INVENTOR WINTHROP in 00x45 WARREN .1 MERBOTH AT TORNE Y Patented July 7, 1953 DEVICE FOR JET PROPULSION THROUGH WATER Winthrop K. Coxe, Covina, and Warren J. Merboth, Arcadia, Califl, assignors, by mesne assignments, to Aerojet-General Corporation, Cincinnati, Ohio, a corporation of Ohio Application April 29, 1948, Serial No. 23,954

4 Claims.

This invention relates to the jet propulsion of a device through a liquid medium and has for its principal object to provide relatively simple equipment for efiiciently and effectively operating a device or craft through water by jet propulsion.

In the copending application of Calvin A. Gongwer et al., Serial No. 737,928, filed March 28, 1947, issued September 19, 1950, as Patent No. 2,522,945 and assigned to the same assignee as the present application, there is disclosed and QFFICE 2 a succession of gas bubbles and water slugs are forced through the exhaust opening with a correspondingintermittent entrance of water into the duct through the inlet valve.

Each explosion of fuel-air mixture produces a bubble of gas under pressure in the duct which claimed a jet-propelled device adapted to opervided a combustion chamber into which is sent a The gases of combustion burning fuel mixture. escaping under pressure from the combustion chamber force the water on out the exit opening at high velocity to develop the propulsive thrust.

In this arrangement, the provision of the comcloses the inlet valve while pushing the slug of water to the exit opening. The momentum of the slug of water in a rearward direction lowers the pressure of the gas bubble behind it, and hence the pressure at the inlet valve is lowered sulficiently to cause the valve to open and let in a new slug of water. At the same time, this underpressure draws a new charge of fuel-air mixture into the combustion chamber from the carburetor. Combustion of this new charge then forcees another slug of water rearwardly through the duct, like the preceding slug. The successive accelerations of these masses of water develop the propulsive thrust for the device.

The foregoing and other features of the invention will be better understood from the following detailed description and the accompanying drawbustion chamber enables gas bubbles effectively to be formed periodically toeject the water.

By our present invention, we provide an arrangement which is an improvement over that disclosed in the said Gongwer et a1. application,

in that we are able to dispense with the need 1.:

chamber. The flap serves eifectively to separate '1";

the gases in the combustion region from the water in the duct during the part of a cycle when there is a low pressure in the combustion region, while allowing free egress of the gases into the duct during the part of the cycle when the gases are under pressure. By this arrangement, the ignition device, ordinarily a spark plug, is never wetted, and the danger of quenching the burning gases by water in the combustion region is avoided.

The flap valve, moreover,v also serves to form a good gas-water interface for the expanding gas bubble formed in the duct. By timing the explosions, and hence the entry of gases into the duct,

ings, of which:

Fig. 1 is a longitudinal view partly in crosssection, showing a jet propelled device in accordance with this invention;

Fig. 2 is a cross-section view taken on the line 2--2 of Fig. 1 showing the position of the flap valve;

Fig. 3 is an enlarged view showing the manner in which the flap valve covers the combustion chamber; I

Fig. 4 is a schematic view showing a motor like that of Fig. 1 in conjunction with an electrical system for timing the explosions.

Fig. 5 is an isometric view of a valve blade used in the forward end of the device of Fig. 1;

Fig. 6 is an isometric view, partly broken, taken from above and showing the manner in which the valve blade covers the valve channel;

Fig. '7 is an end plan View, partly in cross section, showing one of the valve blades interleaved between two valve channels; and

Fig. 8 is a cross section view of the valve assembly taken at line 8-8 of Fig. 1.

Referring to the drawings, the jet motor comprises a duct [0 having an inlet opening or mouth II, at' the front end, and an exhaust opening or nozzle l2 at the rear end. Within the inlet opening there is located a valve assembly [3; and a combustion chamber l4 enters the duct downstream of the valve. At the forward portion where the Valve I3 is located, the cross section of the duct is approximately square or rectangular. as shown in Figs. 1 and 8 and from the rear of the valve the duct tapers at region |5 to a smaller cross section and becomes a circular cross section at region Hi, from whence an elongated pipe portion H of smaller diameter than I6 extends rearwardly to the exhaust opening 12. Preferably the length of the pipe portion should be at least about five times its diameter.

The fuel combustion or firing chambers l4 enters the duct at a position just downstream of the tapered region I5 and has its upper end fitted tothe output end of a valve housing 20, the input end of which is attached to a fuel-air carburetor 2 I. At the place where the combustion chamber enters the duct there is a flap valve 50 held in place by a keeper bar 5|, clamping the forward edge of the flap valve. This valve is ordinarily closed and covers the outlet of the combustion chamber into the duct. The flow of water through the duct has the effect of closing this valve; At times when the pressure in the combustion chamber exceeds that in the duct, the flap valve is pushed open to allow the products of combustion. from the combustion chamber to enter the duct. The flap 50 should be made of a tough flexible material, for example, rubber, fabric, plastic, or other like substance.

The carburetor 'may be of a conventional type such as is commonly employed with internal combustion engines. The valve housing 20 is provided with an internally located valve seat 22 on which is seated a-pop-pet valve 23 which is normally held in a closed position against the seat by a coil spring 24. Through the combustion chamber wall there is inserted a suitable form of ignition device such as a spark plug 25 to ignite the carbureted mixture that has entered the combustion chamber through the valve 23.

A suitable construction for the water inlet valve at'the entrance to the duct is shown in detail in Figs. 5, 6, '7 and 8. The valve is of. the flutter or blade type, and is built up of an assembly of alternating flexible blades 30 and rigid channel members 3|. Each channel member 3| comprises a rectangular late 32, the upper surface of which is providedwith a series of partition members 33, which are preferably integral with the plate 32 and run parallel to each other as shown. These partition members form a series of channels. 34 preferably tapering in depth. They are deeper at the leading edge 35 and diminish to nothing at the rear end 36 to coincide with the thickness of rear edge of blade 3|].

In assembling the valve unit |3 several flexible blades 38 are alternately interleaved between the several channel members 3| and are firmly held near their leading edge 35 by the channel plate 32 of one channel member and the upper edge of partitions 33 of the adjacent channel member.

These valves and rigid channel members are securely held together in a valve housing 31 by bolts 38 which pass through the holes 39 provided in both the flexible blades 30 and the. rigid channel members 3| as shown in Figs. 5 and 8. The central span of the valve assembly is placed. in compression by a series of compression bolts 40 which press against a bearing plate 4|. Valve housing 31 is shown as rectangular for convenience only, and may be of any other suitable shape.

When a series of these valves and channel members ar assembled in the housing to form a complete valve assembly |3 they completely fill the cross section of the duct. For purpose of assembly, the completed valve slides into the housing 31 and is clamped into position by bolts 38, compression bolts 40 and a pair of shouldershaped retainers 42 which are attached to the forward portion of the sides of duct opening A valve of the character just described as the valve l3 for use in the duct, is shown in United States Patent No. 2,432,213, issued December 9, 1947.

Figs. 6 and 7 are views illustrating the means by which one of the valve blades is sandwiched between two of the channel members.

Fig. 6 shows a cutaway view looking into the channel member 3| showing its relationship to valve blade 30. The arrangement is such that each flexible blade is able to vibrate; the lower face 43 alternately contacting and moving away from the top edge 44 of partition 33. This creates the valve action placing the valve in a closed position whenever the pressure on the downstream side of the valve assembly exceeds the pressure acting from the upstream side and permitting flow of liquid through the valve. when the pressure on the upstream side of the valve exceeds that of the downstream side pushing the blade away from the top of channel partition .33.

The timing of the firing may be controlled by an electrical timing system which periodically fires the spark plug. Such systems are well.- known and need not be described in detail here. A suitable form of such a system is shown schematically in Fig. 4. This comprises a timing device 26 placed in series with a vibrator 46 and a coil 41 The timer, vibrator and coil are located between the spark plug. 25 and a. source of electrical energy such as battery 21. The timer 26 may be some suitable sort of time switching arrangement, such as a rotary member having a contact which makes contact with one or more contactpoints during rotation such that the voltage across the battery is periodically applied to the input terminal of the vibrator when the timer contacts are made. Since the vibrator .is in series between the voltage source and the coil, a high tension alternating voltage will be developed at the spark plug 25, while the vibrator is vibrating, all in accordance with well-known spark plug operation. Both the spark plug 25 and the negative terminal of the battery are grounded to complete the circuit.

Operationof the device occurs in the following manner: When the rearwardly moving slug of water causes the pressure within. the duct l0 and combustion chamber M to drop below atmospheric pressure, poppet valve 23 automatically opens and air flows through the carburetor 2|, entraining, atomizing and mixing fuel with it, forming a combustible mixture in the usual manner. This mixture passes through the open valve 23 into the combustion chamber l4, displacing the remaining products of combustion from the previous cycle, while substantially filling the chamber [4 with unexploded mixture and. at the same time relieving the sub-atmospheric pressure in chamber l4. When the pressure in the chamber l4 rises so that it approaches atmospheric pressure, spring 24 will close poppet valve 23. Reducing pressure within the duct I0 likewise causes water to flow through the valve l3 in the same manner in which the fuel-air mixture is drawn in through the carburetor, scavenging the duct and allowing. it to refill with water from the medium. The spark which initiates the explosion starting the succeeding cycle occurs at plug 25, causing the mixture within the. combustion chamber to burn and generate high pressure gases which force open the flap valve and expand through it into the duct l0, generating'a gas bubble under pressure which accelerates the water standing in the duct rearwardly of the fiap valve, as previously described. r

The poppet valve 23 will ordinarily be lightly loaded by the spring 24 to permit it to'open whenever the pressure in the duct drops slightly below atmospheric pressure, thereby allowing the poppet valve to, remain open long enough to permit'a sufficient chargeto pass into the combustion chamber.

The firing periods are controlled by the timer 26 which times the frequency of the spark which initiates the explosion. Preferably, the timing is regulated to approach the natural resonant frequency of the duct. The new charge that'has been drawninto the chamber is therefore fired as soon as the poppet valve automaticallyploses. However, the frequency may be lowered depending on the performance desired. 1

'Theescape of the gases and water from the exhaust opening of the duct at high velocity produces the reactive force which drives the duct forwardly in a well-known manner.

To start the device operating, compressed air from some suitable storage source (not shown) is introduced into the air inlet 48 of the carburetor 2|, while poppet valve 23 is held open by hand. Air passing through the venturi of the carburetor entrains some fuel and the mixture passes into the combustion chamber l4 displacing any water that may be standing in the chamber. The poppet valve is then released and. closes, and the switch on the electrical timing system is closed, firing the charge, and starting the cyclic operation as previously described.

During times when there is under-pressure in the combustion chamber, there would be a tendency for water in the duct to be drawn up into the combustion chamber. Owing to the operation of the flap valve 58, however, this undesired entry of water into the combustion chamber is prevented. Thus the flap valve by its operation closes when the duct water is flowing past it, and it does not open until the pressure in the combustion chamber is higher than in the duct due to the explosion.

By reason of the use of the flexible flap 50, water is kept away from the spark plug, such water at the plug having been a source of trouble in the operation of fiapless devices. Perhaps even more important, the presence of the flap valve avoids the introduction of a mass of finely divided water in the combustion chamber at the time of firing. If such water .were present, it would soak up a considerable amount of energy from the burning gases, which would represent a loss of useful work. An additional advantage of the flap resides in its function of aiding the formation of an especially effective gas-water interface for the expanding bubble as it forms in the duct. Thus the use of the fiap greatly increases the thermodynamic efficiency of the device. It has been found that by the use of the flap the thermodynamic efficiency of this type of reaction motor has been increased by a factor of three or four and the amount of thrust produced by it has been doubled as compared with similar devices which were not provided with the flap;

From the foregoing description of the construction and operation of ourdevice, it should be understood that we have provided a significant improvement in jet propelled ducts, involving a simple construction capable of high eificiency operation and large thrust. The invention should not be construed to be limited to the particular embodiments illustrated and described, which are given for purposes of illustration rather than of limitationga'nd the invention is not limited except in accordance with the scope of the appended claims. 7

l; A jet propulsion motor adapted for operation through water, said motor comprising a duct having an inlet opening and an exhaust opening, anautomatically pressure-operable inlet valve located within the duct for intermittently passing water entering the duct through the inlet opening in a downstream direction only, a combustion chamber, a fuel-air mixing carburetor having an outlet leading into the combustion chamber for admitting into said chamber a carbureted mixture, an automatically pressure operable valve located between said carburetor and said chamber, and firing means for firing the carbureted charge in said chamber, an exit from the chamber into: the side ofthe' duct at a position downstream from the inlet opening, a flexible flap valve positioned at the exit from said chamber into the duct and operable to open to admit the products of combustion into the duct when the pressure within the chamber is greater than that in the duct and to close to prevent water from entering the chamber from the duct when water is passing through the duct past the flap valve, said flap valve, when closed, lying fiat against the inner wall of the duct so as to introduce substantially no resistance to the fiow of water through the duct, whereby firing of the firing device fires. the fuel mixture in the combustion region causing a pressurized gas mass to pass the flap valve into the duct and close the inlet valve and expand rearwardly through the duct, pushing a mass of water toward the exhaust opening.

2. A jet propulsion motor according to claim 1. in which the length of the duct between the entry of the combustion chamber outlet and the exhaust opening is at least five times the diameter of the duct.

3. A jet propulsion motor adapted for operation through water, said motor comprising a duct having an inlet opening and an exhaust opening, an automatically pressure-operable inlet valve located within the duct for intermittently passing water entering the duct through the inlet opening in a downstream direction only, a combustion chamber, a fuelair mixing carburetor having an outlet leading into the combustion chamber for admitting into said chamber a carbureted mixture, an automatic pressure-oper able poppet valve located to admit fuel-air mixture from the carburetor into the combustion chamber when the latter valve is opened but not when the latter valve is closed, timed firing means for firing the carbureted charge in said combustion chamber, an exit from the chamber into the side of the duct at a position downstream from the inlet opening, a flexible flap valve positioned at the entrance of the combustion chamber into the duct, said flap valve, when closed, lying flat against the inner wall of the duct so as to introduce substantially no resistance to the flow of water through the duct, whereby fuel-air mixtures are intermittently drawn from the carburetor through the poppet valve into the combustion chamber and fired intermittently and the expanding gases and combustion products enter the duct in intermittent masses under pressure, forming bubbles of; gas under pressure in the water within the duct, thereby creating intermittent pressurizations in the duct which drives slugs of Water intermittently downstream through the duct and out the exhaust opening during the periodsofpressure when the two valves are automatically closed, and admitting masses of water into the duct intermittently during intervals between the pressure intervals.

4. Ajet propulsion motor adapted for operation through water, said motor comprising-a duet having an inlet opening and an exhaust opening, an automatic pressure-operable valve located within the duct for intermittently passing water entering the duct through the inlet opening in a,- downstream direction only, acombustion shame ber'having an outlet opening into the duct somewhat downstream of said valve and leading into the side of the duct, a flexible flap valve fastened at the position Where the outlet opening enters the duct with the fastening at the upstream side of the flap valve, said flap valve, when closed, lying flat against the inner wall of the duct and coverin said outlet opening, and when open, extending into the duct. from its fastening, wherebypressurized masses of gas from the combustion are forced past the flap valve and drive masses of water intermittently downstream through the duct and. out the exhaust opening during periods of pressure.

WINTI-IROP K. COXE.

WARREN J. MERBOTH.

References Cited in the file of this patent UNITED STATES PATENTS Number N me. Dat

..6.'l ,l,64, Villar v June 11, 1901 9.33% Orr May 9, 1905 1,054,615 Rauch Feb. 25, 1913 2,463,820 Stafford et al. Mar. 8 1949 2,522,945 Gongwer et a1. V Sept. 19, 1950 FOREIGN PATENTS Number Country Date 70,527 Sweden Dec. 3, 1927 82,929 Sweden Apr. 22, 1931 

